1. Field of the Invention
This invention relates to an apparatus for classifying objects by sedimentation, more particularly to an apparatus in which a classifying is performed by using final sedimentation velocity of objects to be classified mixed within fluid and there is provided a bubble-removing passage for removing bubbles within fluid of a classifying bath.
2. Description of the Prior Art
In conventional methods for classifying minute objects of powdery particles, it has been used an apparatus for classifying objects so as to classify the objects to make groups being different in size or density by use of the difference in their sedimentation velocity in fluid.
FIG. 7 shows an example of an apparatus for classifying objects by sedimentation which has been disclosed in the Japanese Patent Application laid-Open No. 6-328002. In the drawing, a first cone-shaped pipe passage 115 is mounted on one side of an opening end of a classifying bath 104 through a flange 105 thereof. The first cone-shaped pipe passage 115 is gradually, widely opened toward the classifying bath 104 in the degree that the fluid does not become turbulence in the case of watching from the pointed end portion.
A second cone-shaped pipe passage 117 a tip 117a of which is opened, is mounted on the other opening end of the classifying bath 104 through the flange 105. The second cone-shaped pipe passage 117 is also gradually, widely opened toward the classifying bath 104 in the degree that the fluid does not become turbulence in the case of watching from the pointed end portion.
A pipe 101 is mounted detachably on the pointed end portion of the first cone-shaped pipe passage 115 and further a pipe 113 is also mounted on the pointed end portion of the second cone-shaped pipe passage 117. A drain 118, a pump 119, an amount of flowing adjusting valve 120, and a flowmeter 121 are arranged in sequence along the line from the pipe 113 to the pipe 101. A straightening lattice 116 is arranged in the neighborhood of the one opening end of the classifying bath 104. The straightening lattice 116 is arranged so as to avoid turbulence by straightening a fluid flowing therein from the first cone-shaped pipe passage 115. A throwing hole 104a is provided to throw objects to be classified therein at the upper part of neighboring said one opening end of the classifying bath 104 and a pipe 127 extending toward the vertical direction is connected to the throwing hole 104a. A boll valve 129 is arranged in the center part of the pipe 127, and a container (not illustrated), in which a suspension including minute objects of lumps of cells to be classified is accommodated, is connected to the upper end thereof.
A plurality of partitioning portions 106 (106a, 106b, . . . ) which narrow downward are provided at the lower part of the classifying bath 104. A respective half union 107 is connected to the lowest part of the partitioning portion 106.
An operation of the apparatus will be described as follows: The inside of the apparatus is filled with the fluid which is circulated within the apparatus by means of the pump 119. In the drawing, the fluid flows from left to right within the classifying bath 104.
In an example, the operation is explained in that the minute objects to be classified are lumps of cells, and fluid is culture. First, lumps of cells fall freely through the pipe 127 and are supplied to the classifying bath 104. At this time, in a relationship between density of culture as a fluid and that of lumps of cells, since density of lumps of cells is a little larger than density of culture accordingly, gravity, buoyancy and frictional resisting power which are subjected to lumps of cells immediately after falling, are in harmony with one another with the result that falling lumps of cells within the fluid promptly fall at the same velocity. This velocity is the final sinking velocity.
The lumps of cells reach the final sinking velocities before falling into the classifying bath 104 while falling through the pipe 127, from this time falling at the same velocity. The lumps of cells within the classifying bath 104 fall with drawing a line of oblique downward direction as shown in the drawing, then entering into the partitioning portion 106 (106a, 106b . . . ) at the lower part of the classifying bath 104, and being classified. At this time, the more lumps of cells have large configuration and have faster final sinking velocity, the more entering into the left partitioning portion 106a, and the more lumps of cells have small configuration and have slower final sinking velocity, the more entering into the right partitioning portion 106b. Thus the lumps of cells are capable of classifying selectively according to size or shape, namely the growing stage. The lumps of cells which enter each of the partitioning portion 106 are moved to the next stage passing through the tube 108 made of silicon.
In FIG. 8, a straightening mesh 136 which is of a mesh less than 5 mm degrees, is used rather than the straightening lattice 116 as the straightening passage of the classifying bath 104. In the drawing, three sheets of straightening meshes 136 are arranged at intervals.
Next, a sample supplying device for the conventional apparatus for classifying by sedimentation will be explained based on FIG. 9 and FIG. 10. In the same drawing, reference numeral 202 designates a classifying bath of the apparatus for classifying by sedimentation which is the same as the classifying bath disclosed in the above-stated Japanese Patent Application Laid-Open No. 6-328002. Besides, a sample supplying portion 201 is mounted on the upper portion of the classifying bath 202. The sample supplying portion 201 is formed in the shape of cylinder or polygonal cylinder. An outflow pipe 206 is mounted on the upper position of the sample supplying portion 201, an opening portion thereof is opened upside down. The other end of the outflow pipe 206 is reached within the culture fluid of the cultivating tank 203 through the pump 204 and a flow rate variable type pinch cock 207, and both of the outer flow pipe 206 and the sample inflow pipe 205 are filled with the same fluid as the culture fluid of the cultivating tank 203.
In the apparatus having above-described construction, cultivated lumps of cells which are cultivated within the cultivating tank 203, are forwarded with pressurization by means of pump 204 from a pointed end portion 205a to the sample supplying portion through the sample inflow pipe 205 together with the fluids including culture fluid. For this reason, upward flow is created within the sample supplying portion 201. The velocity of a flowing fluid thereof is adjusted by the pointed end portion 205, the inside diameter of the outflow tube 206, the sample supplying portion 201, the flow rate of pump 204 and the flow rate variable type pinch cock 207. The velocity of a flowing fluid thereof is adjusted in such a way that the velocity is a little faster than the sinking velocity of lumps of immature cultivated cells in the fluid.
As shown in FIG. 10, therefore, only the immature samples flow upward in the sample supplying portion 201 to flow out into the outflow pipe 206, while, the sample to be classified may sink against the upward stream to come into the classifying tank 202. The immature samples having flown out from the outflow pipe 206 are returned to, via the pump 204 and the flow-rate variable type pinch cock 207, to the culture tank so as to be cultivated again.
However, in the conventional apparatus for classifying by sedimentation as described above, wherein at least one straigthening mess in which the meshes are less than 5 mm each is installed as the straighthening passage causing the classifying apparatus to operate with a laminar flow within the classifying bath, with air that is left in the classifying bath, the pipe, or the pump, extremely minute bubbles dispersed in the colloidal state within the fluid, and gas dissolved within the fluid becomes a visible mass of air with an elapse of time, and the mass of air is stirred by means of pump so that it becomes minute bubbles which flow into the classifying bath, as shown in FIG. 8. The minute bubbles cause clogging on account of adhesion thereof particularly on the upper portion of the fluid passage. As the result thereof, the velocity of fluid as is indicated by the arrow in the drawing, since the flow rate of the upper portion of the classifying bath becomes slow, and the lower portion thereof becomes fast, it can not keep the laminar flow within the classifying bath, in some cases, the sample becomes incapable of classifying accurately.
Furthermore, the bubbles which have entered into the classifying bath collect at the upper portion thereof, entering into the sample supplying portion arranged at the upper part of the classifying bath as shown in FIGS. 9 and 10, the pipe of the sample supplying portion is closed by air lock and so forth, in some cases the samples become incapable of feeding therein.